Viral Transmission and Entry
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Questions and Answers

Which step is not involved in viral pathogenesis?

  • Entry and primary replication
  • Host immune response
  • Cellular injury
  • Viral mutation (correct)

    • What does viral shedding pertain to in viral pathogenesis?

  • Viral entry into host cells
  • Viral spread within the host
  • Host immune response to viral infection
  • Shedding of infectious virus into the environment (correct)

    • What does it mean if a strain of a virus is more virulent than another strain?

  • It has a higher rate of mutation
  • It commonly produces more severe disease in a susceptible host (correct)
  • It has a longer incubation period
  • It spreads faster within the host

    • What is the difference between viral virulence in intact animals and cytopathogenicity for cultured cells?

    <p>Virulence in intact animals refers to the ability to cause disease, while cytopathogenicity refers to the ability to infect cells</p> Signup and view all the answers

    When does viral shedding usually occur in viral pathogenesis?

    <p>At different stages of disease depending on the particular agent involved</p> Signup and view all the answers

    Which of the following is NOT a virus-encoded mechanism for modulation of NK cell activity?

    <p>Upregulation of MHC I on infected cell</p> Signup and view all the answers

    Which pathway does NOT activate the complement system?

    <p>Antigen-presenting pathway</p> Signup and view all the answers

    What is the main focus of B lymphocytes in the immune response?

    <p>Releasing antibodies</p> Signup and view all the answers

    What is the role of T lymphocytes in cell-mediated immunity?

    <p>Directly eliminating pathogens or infected cells</p> Signup and view all the answers

    Which cells have inhibitory and activating receptors to monitor the presence of viral infection?

    <p>NK cells</p> Signup and view all the answers

    What is the process that occurs when interferons are released and bind to IFNAR receptors?

    <p>Activation of JAK-STAT pathway</p> Signup and view all the answers

    Which type of IFNs induce local signaling system and help to establish antiviral response?

    <p>Type I (α/β)</p> Signup and view all the answers

    What is the role of 2’,5’-oligo A synthetase activated by dsRNA?

    <p>Promotes production of oligo A which activates RNase L</p> Signup and view all the answers

    What is the effect of the inflammatory cytokines IL-1, IL-6, TNF-α in response to viral infection?

    <p>Signal sentinel cells to go to the site of infection</p> Signup and view all the answers

    Which proteins are part of the innate immune response and activate the adaptive immune response?

    <p>Macrophages, dendritic cells, natural killer cells</p> Signup and view all the answers

    Which type of infection occurs when a virus crosses the placenta during pregnancy?

    <p>Transplacental infection</p> Signup and view all the answers

    What is the main route for viral spread in the body?

    <p>Bloodstream and lymphatics</p> Signup and view all the answers

    Which type of cells can be used by the virus to enter organs through transcytosis?

    <p>Capillary epithelial cells with sinusoids/fenestrations</p> Signup and view all the answers

    What determines the pattern of systemic illness during a viral infection?

    <p>Viral tropism</p> Signup and view all the answers

    How do viruses like HPV access the body?

    <p>Infecting genital epithelium</p> Signup and view all the answers

    Which type of immune response does the host's recognition of Toll-like receptors (TLRs) and NOD-like receptors (NLRs) activate?

    <p>Innate immune response</p> Signup and view all the answers

    What is the function of cytoplasmic RNA helicase MDA5 in the host immune response to viral infections?

    <p>Detecting specific types of viral RNA</p> Signup and view all the answers

    How does the rabies virus evade the immune response and enter the blood-brain barrier (BBB)?

    <p>By using Diapedesis/Trojan Horse Approach</p> Signup and view all the answers

    What type of viral spread occurs through lytic and lysogenic responses during replication?

    <p>Horizontal spread</p> Signup and view all the answers

    What is the role of protein kinase R (PKR) in the host immune response to viral infections?

    <p>Serving as a sensor for viral dsRNA and inhibiting cap-dependent translation</p> Signup and view all the answers

    Which type of transmission involves the transmission of virions in respiratory droplets?

    <p>Direct transmission</p> Signup and view all the answers

    Which part of the body is the most common portal of entry for viruses into the human body?

    <p>Respiratory tract</p> Signup and view all the answers

    Which type of cells are less abundant in the lower respiratory tract compared to the upper respiratory tract?

    <p>Goblet cells</p> Signup and view all the answers

    Which specialized cells play roles in immune surveillance and defense in the gastrointestinal tract?

    <p>M cells and Paneth cells</p> Signup and view all the answers

    Which type of viruses contain capsid proteins that are not denatured by low pH?

    <p>Acid-resistant viruses</p> Signup and view all the answers

    What is the term for the time at which an infected individual is infectious to contacts?

    <p>Viral shedding</p> Signup and view all the answers

    Which term refers to a virus being pathogenic for a particular host if it can infect and cause signs of disease in that host?

    <p>Viral virulence</p> Signup and view all the answers

    What does the term 'cytopathogenicity' for cultured cells refer to?

    <p>Ability to lyse cells in vitro</p> Signup and view all the answers

    Which step in viral pathogenesis involves the entry and primary replication of the virus?

    <p>Entry and primary replication</p> Signup and view all the answers

    What is the term for the last stage in viral pathogenesis, representing the time at which an infected individual is infectious to contacts?

    <p>Viral shedding</p> Signup and view all the answers

    Which enzyme dephosphorylates the Phosphate group of specific MAMPS recognized by the card domain?

    <p>PP1a</p> Signup and view all the answers

    What is the role of TRIM25 and Riplet in the ubiquitination process of CARD domains?

    <p>Facilitate the ubiquitination of CARD domains</p> Signup and view all the answers

    What is the function of MAVS in the context of ubiquitinated CARD domains?

    <p>Facilitate the aggregation of ubiquitinated CARD domains</p> Signup and view all the answers

    What is the consequence of IKK homodimerization and phosphorylation of IKB?

    <p>Induces the stabilization of IRF</p> Signup and view all the answers

    What activates the IRF by phosphorylating and stabilizing them?

    <p>TBK</p> Signup and view all the answers

    Which pathway does NOT activate the complement system?

    <p>Viral pathway</p> Signup and view all the answers

    Which type of cells mediate humoral immunity in the immune response?

    <p>B lymphocytes</p> Signup and view all the answers

    What is the role of MHC I on a normal cell in relation to NK cells?

    <p>It inhibits NK cells from killing normal cells</p> Signup and view all the answers

    What is the main focus of T lymphocytes in the immune response?

    <p>Directly eliminating pathogens or infected cells</p> Signup and view all the answers

    Which type of cells can monitor the presence of viral infection via uptake of apoptotic bodies of infected cells?

    <p>Macrophages</p> Signup and view all the answers

    Which type of cells are used by the virus to enter organs through transcytosis?

    <p>Endothelial cells with tight junctions</p> Signup and view all the answers

    What is the main route for viral spread in the body?

    <p>Bloodstream and lymphatics</p> Signup and view all the answers

    What is the difference between transplacental infection and perinatal infection?

    <p>Timing of the viral entry into the child's body</p> Signup and view all the answers

    What determines the pattern of systemic illness during a viral infection?

    <p>Viral tropism</p> Signup and view all the answers

    How do viruses like HPV access the body?

    <p>Infecting genital epithelium</p> Signup and view all the answers

    Which of the following is an example of direct transmission of a virus?

    <p>Transmission of virions in respiratory droplets</p> Signup and view all the answers

    What is the role of neuraminidase in the entry of the influenza virus into the human body?

    <p>Cleaving sialic acid for entry</p> Signup and view all the answers

    Which part of the body provides a large surface area for virus interaction, making it the most common portal of entry for viruses into the human body?

    <p>Respiratory tract</p> Signup and view all the answers

    What is the function of mucus-secreting goblet cells in the respiratory tract?

    <p>Serving as a physical and chemical barrier</p> Signup and view all the answers

    What must viruses entering via the gastrointestinal tract be resistant to in order to successfully survive and replicate in the immune cells?

    <p>Low pH, bile, and enzymes</p> Signup and view all the answers

    Which type of receptors recognize MAMPs and activate transcription factors to promote the expression of IFNs and inflammatory cytokines?

    <p>Toll-like receptors (TLRs)</p> Signup and view all the answers

    What is the function of cytoplasmic RNA helicase RIG-1 in the host immune response to viral infections?

    <p>Detecting specific types of viral RNA</p> Signup and view all the answers

    What is the main route for viral spread from one organism to another?

    <p>Through various body fluids</p> Signup and view all the answers

    Which step is involved in the intrinsic immune response to a pathogen?

    <p>Mediated by proteins that detect and eliminate pathogens</p> Signup and view all the answers

    What type of immune response does the immune system mount in response to viral infections?

    <p>Innate (nonspecific) and Adaptive (specific) immune responses</p> Signup and view all the answers

    Viral pathogenesis refers to how a virus causes a ______

    <p>disease</p> Signup and view all the answers

    A strain of a certain virus is more ______ than another strain if it commonly produces more severe disease in a susceptible host

    <p>virulent</p> Signup and view all the answers

    Viral shedding pertains to the shedding of infectious virus into the environment, which is the ______ stage in viral pathogenesis

    <p>last</p> Signup and view all the answers

    Viral shedding usually occurs from the body surfaces involved in viral entry and occurs at different stages of disease depending on the particular ______ involved

    <p>agent</p> Signup and view all the answers

    A virus is pathogenic for a particular host if it can infect and cause signs of ______ in that host

    <p>disease</p> Signup and view all the answers

    NK cells release enzymes that will induce a caspase signalling cascade and induce cell death to ______ cell

    <p>infected</p> Signup and view all the answers

    3 pathways activating complement system: classical, lactin, and alternative ______

    <p>pathway</p> Signup and view all the answers

    The Complement System is composed of serum proteins that form a cascade ultimately resulting in the enhancement of ______ response

    <p>immune</p> Signup and view all the answers

    macrophages, dendritic cells) are ______

    <p>phagocytes</p> Signup and view all the answers

    B lymphocytes - mediates humoral immunity; focuses on eradicating virus particles via ______, release antibodies

    <p>neutralization</p> Signup and view all the answers

    Direct transmission includes transfer of the virus by direct contact or droplet spread, with direct contact involving skin-to-skin contact, sexual intercourse, or kissing, and droplet spread involving the transmission of virions in respiratory ______.

    <p>droplets</p> Signup and view all the answers

    The respiratory tract is the most common portal of entry for viruses into the human body, with the mucosal surfaces providing a large surface area for virus ______.

    <p>interaction</p> Signup and view all the answers

    Influenza virus is an example of a virus that enters via the respiratory tract, developing ways to overcome the host’s defenses and utilizing neuraminidase to cleave sialic acid for ______.

    <p>entry</p> Signup and view all the answers

    The upper respiratory tract contains abundant goblet cells that produce mucus, serving as a physical and chemical barrier and lined with cilia that move to push mucus and trapped contents to the ______.

    <p>throat</p> Signup and view all the answers

    Viruses entering via the gastrointestinal tract must be resistant to the low pH, bile, and enzymes present in the hostile environment, with successful viruses being able to survive and replicate in the immune ______.

    <p>cells</p> Signup and view all the answers

    Host Immune Response and Viral Spread1. The immune system responds to viral infections through ______ (nonspecific) and Adaptive (specific) immune responses.

    <p>Innate</p> Signup and view all the answers

    Intrinsic cell response to MAMPs involves recognition of specific macromolecules shared among microorganisms, such as dsRNA, peptidoglycan, LPS, and ______.

    <p>flagellin</p> Signup and view all the answers

    Protein kinase R (PKR) serves as a sensor for viral dsRNA and inhibits cap-dependent translation by ______.

    <p>eIF2α</p> Signup and view all the answers

    Host receptors, such as Toll-like receptors (TLRs) and NOD-like receptors (NLRs), recognize MAMPs and activate transcription factors to promote the expression of ______ and inflammatory cytokines.

    <p>IFNs</p> Signup and view all the answers

    Viral spread occurs through Lytic and Lysogenic response during replication, with defense mechanisms inhibiting virus ______.

    <p>replication</p> Signup and view all the answers

    Viral spread in the body occurs via the bloodstream or ______ (viremia) and neural spread through neurons.

    <p>lymphatics</p> Signup and view all the answers

    Many viruses produce disease at sites distant from their entry point by disseminating within the ______.

    <p>host</p> Signup and view all the answers

    Capillary epithelial cells with sinusoids/fenestrations can be used by the virus to enter organs through ______ or replicate inside the cells.

    <p>transcytosis</p> Signup and view all the answers

    Congenital infections occur when a virus crosses the placenta during ______, leading to long-term virus persistence in the child.

    <p>pregnancy</p> Signup and view all the answers

    HIV is more likely transmitted in male-female than ______ sexual contact.

    <p>male-male</p> Signup and view all the answers

    RIG1, MDA5, cGAS, TLR, TRIF, and Myd88 activate ______ and IRF which induce expression of interferons (type I)

    <p>NFKB</p> Signup and view all the answers

    Interferons when transcribed and released, they bind to interferon receptors which induce transcription of ______; positive feedback

    <p>PKR</p> Signup and view all the answers

    Once it recognizes dsRNA, PKR phosphorylates eiF2-GDP but not where it is supposed to be. This inhibits GDP to become GTP. This inhibits ______

    <p>translation</p> Signup and view all the answers

    When interferons are released, they bind to IFNAR receptors which will activate ______ pathway

    <p>JAK-STAT</p> Signup and view all the answers

    Jak and Tyk can autophosphorylate each other’s tyrosines. They phosphorylate and activate Stat protein which activates IRF. IRF binds to ISRE (IFN-sensitive response element) that will induce expression of more ______ or other genes like PKR

    <p>interferons</p> Signup and view all the answers

    Study Notes

    Modes of Viral Transmission and Entry into the Human Body

    • In some viral infections, such as rabies, humans represent dead-end infections, and shedding does not occur.
    • Direct transmission includes transfer of the virus by direct contact or droplet spread, with direct contact involving skin-to-skin contact, sexual intercourse, or kissing, and droplet spread involving the transmission of virions in respiratory droplets.
    • Indirect transmission involves the presence of an intermediary between hosts, including airborne transmission carried by dust or aerosolized particles and transmission via fomites or vectors such as mosquitoes and ticks.
    • For host infection to occur, a virus must first attach to and enter cells of the body surfaces—skin, respiratory tract, gastrointestinal tract, or urogenital tract.
    • The respiratory tract is the most common portal of entry for viruses into the human body, with the mucosal surfaces providing a large surface area for virus interaction.
    • Influenza virus is an example of a virus that enters via the respiratory tract, developing ways to overcome the host’s defenses and utilizing neuraminidase to cleave sialic acid for entry.
    • The upper respiratory tract contains abundant goblet cells that produce mucus, serving as a physical and chemical barrier and lined with cilia that move to push mucus and trapped contents to the throat.
    • In the lower respiratory tract, smaller aerosolized particles or liquids can travel, with mucus-secreting goblet cells being less abundant and ciliated cells present at the beginning but absent in the alveoli of the lungs.
    • The gastrointestinal tract, stretching from the mouth to the anus, contains fingerlike projections called villi, lymph node–like masses called Peyer’s patches, and specialized epithelial cells such as M cells and Paneth cells that play roles in immune surveillance and defense.
    • Viruses entering via the gastrointestinal tract must be resistant to the low pH, bile, and enzymes present in the hostile environment, with successful viruses being able to survive and replicate in the immune cells.
    • The host provides protection against viruses entering through the gastrointestinal tract, such as saliva containing enzymes and antibodies, stomach acid, and bile, which can break down and denature viruses.
    • Acid-labile viruses are easily destroyed in acidic environments, while acid-resistant viruses contain capsid proteins that are not denatured by low pH. For example, Rhinoviruses are acid labile, whereas Poliovirus is acid resistant within the Picornaviridae family.

    Host Immune Response and Viral Spread

    • Rabies virus uses Diapedesis/Trojan Horse Approach to infect immune cells and enter the BBB.
    • Directional release allows the virus to evade immune response by infecting neighboring cells and polarized release for epithelial cells.
    • Viral spread occurs through Lytic and Lysogenic response during replication, with defense mechanisms inhibiting virus replication.
    • The immune system responds to viral infections through Innate (nonspecific) and Adaptive (specific) immune responses.
    • Viral spread from one organism to another occurs horizontally through various body fluids and shedding from infected body surfaces.
    • Shedding of viruses occurs at different stages of the disease, representing the time when an infected individual is infectious to contacts.
    • Environmental factors like humidity, temperature, and particle size affect viral transmission.
    • Host receptors, such as Toll-like receptors (TLRs) and NOD-like receptors (NLRs), recognize MAMPs and activate transcription factors to promote the expression of IFNs and inflammatory cytokines.
    • Intrinsic immune response is the infected cell's response to a pathogen without relying on transcription, mediated by proteins that detect and eliminate pathogens or induce gene transcription.
    • Intrinsic cell response to MAMPs involves recognition of specific macromolecules shared among microorganisms, such as dsRNA, peptidoglycan, LPS, and flagellin.
    • Cytoplasmic RNA helicases RIG-1 and MDA5 function as RNA sensors, detecting specific types of viral RNA.
    • Protein kinase R (PKR) serves as a sensor for viral dsRNA and inhibits cap-dependent translation by eIF2α.

    Viral Entry and Spread in the Body

    • Poliovirus, reovirus, and HIV exploit M cells for entry past the urogenital tract epithelium.
    • Genital tract refers to reproductive organs; sexually transmitted diseases are transmitted via sexual activity.
    • HIV is more likely transmitted in male-female than male-male sexual contact.
    • Viruses like HPV infect genital epithelium, while hepatitis B virus and HIV access the body through breaks or cell receptor binding.
    • The skin, composed of epidermis and dermis, serves as a barrier against virus entry; insect bites and animal bites can also introduce viruses.
    • Congenital infections occur when a virus crosses the placenta during pregnancy, leading to long-term virus persistence in the child.
    • Transplacental infection and perinatal infection are different; C-section minimizes perinatal infection, recommended for mothers with diseases like HIV.
    • Viral tropism determines the pattern of systemic illness during an infection.
    • Viral entry into different organs is determined by cell susceptibility, permissiveness, immune cells, and tissue accessibility.
    • Many viruses produce disease at sites distant from their entry point by disseminating within the host.
    • Viral spread in the body occurs via the bloodstream or lymphatics (viremia) and neural spread through neurons.
    • Capillary epithelial cells with sinusoids/fenestrations can be used by the virus to enter organs through transcytosis or replicate inside the cells.

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    Viral Pathogenesis Lecture 6 PDF

    Description

    Test your knowledge of viral transmission and entry into the human body with this informative quiz. Explore the various modes of viral transmission, including direct and indirect methods, and learn about the specific entry points for viruses into the human body, such as the respiratory and gastrointestinal tracts. Gain insights into how different viruses overcome host defenses and the protective mechanisms the body employs against viral entry.

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